I recently discovered MathJax, a JavaScript library that implements LaTeX equation display. It’s brilliant; we’re now using it in our documentation (it’s bundled with Doxygen) and I plan to make heavy use of it in the future wherever it makes sense. Some samples of its capabilities:

Einstein’s famous equation:

Something a little more complicated (one of the equations implemented in the code I’ve been working on for the last few months):

And now, something more complicated yet (defining the elements in the equation above):

I highly recommend MathJax. I’m currently running it via the MathJax-LaTeX WordPress plugin, which allows you to embed it with handy [​latex]...[​/latex] shortcode syntax.